Field of the Invention
The present invention relates to a resin frame equipped membrane electrode assembly for a fuel cell. The resin frame equipped membrane electrode assembly includes an MEA having different sizes of components, i.e., an MEA including a solid polymer electrolyte membrane and a first electrode and a second electrode having different surface sizes sandwiching the solid polymer electrolyte membrane. Further, the resin frame equipped membrane electrode assembly includes a resin frame member provided around the MEA.
Description of the Related Art
In general, a solid polymer electrolyte fuel cell employs a solid polymer electrolyte membrane. The solid polymer electrolyte membrane is a polymer ion exchange membrane. The fuel cell includes a membrane electrode assembly (MEA) where an anode and a cathode are provided on both sides of the solid polymer electrolyte membrane. Each of the anode and the cathode includes a catalyst layer (electrode catalyst layer) and a gas diffusion layer (porous carbon).
In the fuel cell, the membrane electrode assembly is sandwiched between separators (bipolar plates) to form a power generation cell (unit cell). A predetermined number of the power generation cells are stacked together to form a fuel cell stack. In use, for example, the fuel cell stack is mounted in a vehicle as an in-vehicle fuel cell stack.
In some cases, the membrane electrode assembly has structure where components of the MEA have different sizes, i.e., the surface size of one of gas diffusion layers is smaller than the surface size of the solid polymer electrolyte membrane, and the surface size of the other of the gas diffusion layers is the same as the surface size of the solid polymer electrolyte membrane. In this regard, for the purpose of reducing the amount of expensive material used for the solid polymer electrolyte membranes, and protecting the thin solid polymer electrolyte membranes having low strength, frame equipped MEAs including resin frame members around the solid polymer electrolyte membranes have been adopted.
For example, a membrane electrode assembly disclosed in Japanese Laid-Open Patent Publication No. 2007-066766 is known. In the membrane electrode assembly, an anode catalyst layer and an anode gas diffusion layer are provided on one surface of a membrane, and a cathode catalyst layer and a cathode gas diffusion layer are provided on the other surface of the membrane to form an MEA. The outer sizes of the anode catalyst layer and the anode gas diffusion layer are the same as the outer size of the membrane. The outer sizes of the cathode catalyst layer and the cathode gas diffusion layer are smaller than the outer size of the membrane. Thus, the MEA has different sizes of components.
The surface size of the anode gas diffusion layer is larger than the surface size of the cathode gas diffusion layer. The outer end of the membrane adjacent to the cathode gas diffusion layer and a gasket structural body are joined together through an adhesion portion. In the structure, the outer end of the cathode gas diffusion layer and the inner end of the gasket structure body are positioned to face each other.